The present invention relates to sensing light and sensing the state of a memory cell. Some embodiments relate to current-to-frequency converters including, but not limited to, light-to-frequency converters (LTF converters).
A typical light-to-frequency converter includes a photodiode that produces an electrical current proportional to the amount of light (the number of photons) detected by the photodiode per unit of time. The LTF converter converts the photodiode current to a sequence of electrical pulses of a frequency proportional to the current's magnitude. The pulses can be counted to provide a digital value corresponding to the amount of light per unit of time. See e.g. U.S. Pat. No. 4,465,562, issued Aug. 28, 1984 to Wicnienski et al. and incorporated herein by reference.